The present invention relates to a technique for the measurement of a position in a navigation equipment which is applied to a mobile object such as an automobile.
A prior-art technique for measuring a position in a navigation equipment for an automobile is known from the official gazette of Japanese Patent Application Laid-open No. 316607/1989.
This navigation equipment includes a radio navigation device which measures the position of the automobile by utilizing electric waves transmitted from artificial satellites, and a self-contained navigation device which measures the position of the automobile by using various sensors, road map information, etc. In operation, in a case where the difference between a position measured by the radio navigation device and a position measured by the self-contained navigation device exceeds a preset value, the measured result of the self-contained navigation device or a result obtained by processing this measured result with a predetermined filter is taken as an estimated positional value, which is used for correcting the offset of the measured value of the radio navigation device. To the contrary, in a case where the above difference does not exceed the preset value, the measured result of the radio navigation device or a result obtained by processing this measured result with a predetermined filter is taken as an estimated positional value, which is used for correcting the drift of the measured value of the self-contained navigation device.